4-Oxo-8-(4-phenylbutoxy)benzoylamino!-2-(tetrazol-5-yl)-4H-1-benzopyran.1/ 2 hydrate (common name: pranlukast, hereinafter referred to as "pranlukast" in the specification including the claims) represented by formula: ##STR1## is a compound having a potential antagonistic action against leucotriene C.sub.4 (LTC.sub.4) and leucotriene D.sub.4 (LTD.sub.4) and is expected as a treating agent for allergic bronchial or pulmonary diseases, allergic shock, and various allergic inflammatory diseases.
However, pranlukast is fine powder having very strong adhesiveness. When pranlukast merely mixed with additives is formed into such dose forms as tablets or capsules, the pranlukast powder adheres to a punch, a die, a rotary table and the like, making continuous production difficult.
Improvement on physical properties of strongly adhesive fine powder is generally achieved by increasing the particle size of the raw material powder by agitation granulation, wet screening granulation, fluidized bed granulation, and the like. However, since the properties of powder containing pranlukast that is strongly adhesive fine powder in a high concentration depends on mainly the pranlukast present in a high concentration, an increase in particle size does not lead to improvement in powder properties, and continuous tabletting or capsule-filling is still impossible.
It is known that adhering to machinery can be prevented by (1) a method comprising adding a large quantity of an additive having little adhesiveness and granulating the mixture or (2) a method comprising coating strongly adhesive powder with lactose.
Pranlukast preparations prepared by method (1) are to have an increased size and are not deemed favorable to patients suffering from asthma and the like to whom pranlukast is applied. In fact, if the pranlukast content is reduced to about 10%, granules prepared in a conventional method can be continuously tableted or capsule-filled but only to produce large-sized preparations.
Method (2) is usually carried out by fluidized bed coating. However, the pranlukast powder gets coarse and gains a considerable size during fluidized bed coating, which necessitates a size regulating step. During the size regulating step, the coarse particles are destroyed to expose the drug with adhesiveness, eventually failing to improve the adhesiveness of the granules.
Accordingly, an object of the present invention is to provide pranlukast-containing granules having a narrow particle size distribution and good flow properties by modifying the strongly adhesive surface of pranlukast and to provide a method for producing the same.
Another object of the present invention is to provide pranlukast-containing granules which exhibit satisfactory disintegrating and dispersing properties after administration.